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The first plastic football helmet came in 1940. It was invented and patented by John T. Riddell and his son John T. Riddell Jr., of the John T. Riddell Company in Chicago, a sporting goods provider. The single molded shell was stronger, lighter, longer-lasting, and did not rot the way leather does when damp. Colors could also be baked into the ...
A football helmet is a type of protective headgear used mainly in gridiron football, although a structural variation has occasional use in Australian rules football. It consists of a hard plastic shell with thick padding on the inside, a face mask made of one or more plastic-coated metal bars, and a chinstrap. Each position has a different type ...
The sedimentary rock cover of the continents of the Earth's crust is extensive (73% of the Earth's current land surface), [ 1 ] but sedimentary rock is estimated to be only 8% of the volume of the crust. [ 2 ] Sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks.
These concretions range in size from a few millimeters to as much as 0.7 m (2.3 ft) in length and 12 cm (0.39 ft) in thickness. Most of these concretions are oblate spheroids. Other "pop rocks" are small polycuboid pyrite concretions, which are as much as 7 cm (0.23 ft) in diameter.
Arenite (from the Latin arena, "sand") [1] is a sedimentary clastic rock with sand grain size between 0.0625 mm (0.00245 in) and 2 mm (0.08 in) and containing less than 15% matrix. [2] The related adjective is arenaceous. The equivalent Greek-derived term is psammite, though this is more commonly used for metamorphosed sediments.
The black crystal is garnet, the pink-orange-yellow colored strands are muscovite mica, and the brown crystals are biotite mica. The grey and white crystals are quartz and (limited) feldspar. Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture.
Blueschist on Île de Groix, France Photomicrograph of a thin section of blueschist facies metamorphosed basalt, from Sivrihisar, Turkey. Blueschist (/ ˈ b l uː ʃ ɪ s t /), also called glaucophane schist, is a metavolcanic rock [1] that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures (200–500 °C (392–932 °F ...
A full-size replica of the 1933 Michigan State gold and black winged helmet. Early football helmet designs incorporated panels of leather, which were sometimes manufactured using strips of contrasting color. The Indiana and Michigan State football teams also adopted variations on the design. Michigan State's helmet used a colored stripe ...
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